.TH std::copyable_function 3 "2024.06.10" "http://cppreference.com" "C++ Standard Libary"
.SH NAME
std::copyable_function \- std::copyable_function

.SH Synopsis
   Defined in header <functional>
   template< class... >                                   \fB(1)\fP (since C++26)
   class copyable_function; // not defined
   template< class R, class... Args >

   class copyable_function<R(Args...)>;
   template< class R, class... Args >
   class copyable_function<R(Args...) noexcept>;
   template< class R, class... Args >
   class copyable_function<R(Args...) &>;
   template< class R, class... Args >
   class copyable_function<R(Args...) & noexcept>;
   template< class R, class... Args >
   class copyable_function<R(Args...) &&>;
   template< class R, class... Args >
   class copyable_function<R(Args...) && noexcept>;       \fB(2)\fP (since C++26)
   template< class R, class... Args >
   class copyable_function<R(Args...) const>;
   template< class R, class... Args >
   class copyable_function<R(Args...) const noexcept>;
   template< class R, class... Args >
   class copyable_function<R(Args...) const &>;
   template< class R, class... Args >
   class copyable_function<R(Args...) const & noexcept>;
   template< class R, class... Args >
   class copyable_function<R(Args...) const &&>;
   template< class R, class... Args >

   class copyable_function<R(Args...) const && noexcept>;

   Class template std::copyable_function is a general-purpose polymorphic function
   wrapper. std::copyable_function objects can store and invoke any CopyConstructible
   Callable target — functions, lambda expressions, bind expressions, or other function
   objects, as well as pointers to member functions and pointers to member objects.

   The stored callable object is called the target of std::copyable_function. If a
   std::copyable_function contains no target, it is called empty. Unlike std::function,
   invoking an empty std::copyable_function results in undefined behavior.

   std::copyable_functions supports every possible combination of cv-qualifiers,
   ref-qualifiers, and noexcept-specifiers not including volatile provided in its
   template parameter. These qualifiers and specifier (if any) are added to its
   operator().

   std::copyable_function satisfies the requirements of CopyConstructible and
   CopyAssignable.

.SH Member types

   Type        Definition
   result_type R

.SH Member functions

   constructor   constructs a new std::copyable_function object
   (C++26)       \fI(public member function)\fP
   destructor    destroys a std::copyable_function object
   (C++26)       \fI(public member function)\fP
   operator=     replaces or destroys the target
   (C++26)       \fI(public member function)\fP
   swap          swaps the targets of two std::copyable_function objects
   (C++26)       \fI(public member function)\fP
   operator bool checks if the std::copyable_function has a target
   (C++26)       \fI(public member function)\fP
   operator()    invokes the target
   (C++26)       \fI(public member function)\fP

.SH Non-member functions

   swap(std::copyable_function) overloads the std::swap algorithm
   (C++26)                      \fI(function)\fP
   operator==                   compares a std::copyable_function with nullptr
   (C++26)                      \fI(function)\fP

.SH Notes

   Implementations may store a callable object of small size within the
   std::copyable_function object. Such small object optimization is effectively
   required for function pointers and std::reference_wrapper specializations, and can
   only be applied to types T for which std::is_nothrow_move_constructible_v<T> is
   true.

       Feature-test macro       Value    Std          Feature
   __cpp_lib_copyable_function 202306L (C++26) std::copyable_function

.SH Example

    This section is incomplete
    Reason: example

.SH See also

   function           wraps callable object of any copy constructible type with
   \fI(C++11)\fP            specified function call signature
                      \fI(class template)\fP
   move_only_function wraps callable object of any type with specified function call
   (C++23)            signature
                      \fI(class template)\fP

.SH Category:
     * Todo with reason
